Growth hormone-binding protein levels over one year in healthy prepubertal children: intraindividual variation and correlation with height velocity.
The role of GH-binding protein (GHBP) in growth regulation is still under debate. We investigated 29 prepubertal healthy children (13 girls/16 boys; mean age 9.3 y to study intraindividual variation in serum GHBP and to explore whether any such variation was related to changes in IGF-I, IGF-binding protein-3 (IGFBP-3) or urinary excretion of GH. The relationship between changes in GHBP concentrations, short-term height velocity, and changes in body composition was also studied. Blood samples were taken every month for 1 y, for measurements of GHBP, IGF-I, and IGFBP-3. The mean coefficient of variation in monthly GHBP concentrations in individual children was 18% (range, 6.7-33.0%). The values for each child were normalized by expressing the concentration as a ratio to the mean GHBP concentration. GHBP values were highest in January and lowest in August (22% difference). Maximal monthly changes in GHBP correlated with simultaneous changes in weight (rs = 0.38, p < 0.05) and IGF-I (rs = 0.38, p < 0.05). The mean GHBP concentration during the year correlated with height velocity (rs = 0.37, p < 0.05) and the mean serum concentration of IGF-I (rs = 0.42, p < 0.05) and IGFBP-3 (rs = 0.60, p < 0.001). We conclude that there is a significant monthly variation in GHBP concentrations in healthy prepubertal boys and girls, which is correlated to changes in weight and IGF-I. The mean GHBP concentration during the year is correlated with the mean serum concentrations of IGF-I, IGFBP-3, and with height velocity. Thus, the variation in GHBP concentrations appears to mirror GH sensitivity, because no parallel changes in urinary GH excretion were observed.
Gelander
L
L
International Pediatric Growth Research Centre, Department of Pediatrics, University of Göteborg, Sweden.
Bjarnason
R
R
Carlsson
L M
LM
Albertsson-Wikland
K
K
D001827:Body Height; D002352:Carrier Proteins / Q000097:blood*; D002648:Child; D005260:Female; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D008297:Male; D011627:Puberty; D012016:Reference Values
D002352:Carrier Proteins; D019382:Human Growth Hormone; C051815:somatotropin-binding protein